FIG. 5.

Hemifusion does not occur at IAS. XC cell-bound Mo-MLV was incubated in fusion buffer at 37°C first for 15 min in the presence of 1.2 mM M135 and then for 1 min in the presence or absence of 0.4 mM CPZ. The effect of CPZ on the fusion reaction of nonarrested virus was tested by incubating cell-bound virus first for 1 min in the presence or absence of 0.4 mM CPZ and then for an additional 15 min without the drug. After the incubations, the virus was inactivated by treatment with pH 3 buffer, and the cultures were processed for polykaryon formation to assess fusion efficiencies. These were expressed as percentages of the control, i.e., the virus fused in the absence of drugs. Note the logarithmic scale.